I have nothing obvious left to suggest.
Since you have tested this in your own channel it should work.
And you claim you are getting no NOTICE/USERTNOTICE/errors
I don’t use TMI.js so the next step is to seek help from the library maintainers.
Or try plugging your user token + username into this chat example
Potenitally add a line at 201 of console.log(payload); to log everything that is sent to your process and see whats what.